1. Field of the Invention
The present invention relates to a method and an apparatus for producing a sheet-like (i.e. plate-type or panel-like) insulation support provided with an adhesive layer for a gradient coil of a magnetic resonance device.
2. Description of the Prior Art
Gradient coils for magnetic resonance devices have a number of layers of individual copper coils (windings) that generate gradient fields, with insulating layers and cooling systems therebetween. The insulating layers are formed by a plate-type insulation support. To produce such a gradient coil, the copper coils are first wound in a horizontal form defining the winding geometry. This form has defined grooves, in which the copper conductors are laid to form the coil. The wound conductors project somewhat from the plane of the form, allowing an insulation support to be positioned thereupon and to be attached to the wound coils. The coil windings are fixed by this attachment to the insulation support and can then be removed from the winding form and be bent together with the insulation support attached thereto into a curved shape to form a cylindrical gradient coil.
The insulation support has an adhesive layer that attaches the insulation support to the copper windings. This adhesive layer conventionally is applied to the plate-type insulation support as a reactive, adhesive containing solvent, with the solvent then being evaporated. Defined curing causes the adhesive to change to what is known as the B state, in other words it is partially hardened in place. If the insulation support is now to be attached to the coil windings, the support with the adhesive layer is positioned on the windings and heated, with the result that the adhesive changes to a sticky (tacky) state, after which it finally hardens.
The production and handling of such insulation supports is time-consuming and complex. In particular the fact that the adhesive layer has changed to an already pre-reacted B state permits only a relatively narrow processing time window, during which sufficient adhesion of the adhesive is ensured and therefore a reliable connection to the coil windings is possible. Application of the adhesive is also complex; in particular it is necessary to ensure a uniform layer thickness and it is also essential to prevent air bubbles in the adhesive and toward the insulation support, to ensure the required partial discharge resistance over this coil section.